Muffler for internal combustion engines



'June 7, 1932. F. E. ASELTINE MUFFLER FOR INTERNAL COMBUSTION ENGINES Filed March 8. 1929 Patented June 7, 1932 UNETED s'rA'rss PATENT OFFICE FRED E. ASELTINE, OF DAYTON, OHIO, ASSIGNOR T DELCO PRODUCTS CORPORATION, OF DAYTON, OHIO, A CORPORATION OF DELAWARE MUFFLER FOR INTERNAL COMBUSTION ENGINES Application filed March 8, 1929.

This invention relates to improvements in mufflers for internal combustion engines.

In providing an internal combustion engine with a device for mufiiing the sounds produced by the explosions, it has been found that such devices sometimes cause a back pressure to be exerted which materially affects the power development of the engine.

' If the exhaust gases are permitted to strike the outer shell or casing of the mufiling device with a substantial impact, a metallic, pounding sound, termed shell noise will result.

Operators of engine driven vehicles, when descending a comparatively steep grade, generally use the engine as a braking medium in order notto subject the service brakes to undue wear. When used as a braking medium, the engine is left coupled to the running gear of the vehicle and the throttle is substantially closed. Under these conditions, the vehicle drives the engine at a comparatively high rate, the engine acting as a drag upon the momentum of the vehicle. The engine, when so operated, will set up pulsations in the exhaust line which cause Wh at is termed a high speed coasting roar in the muifling device, the intensity or pitch of said roar being dependent upon the speed of the engine and the construction of the muflling device.

7 It is among the objects of the present invention to provide a. muffler of simple structure and design, which is adapted to suppress or dampen the explosion sounds of an internal combustion engine, without causing any appreciable back pressure to be exerted upon the engine. I

A further object is to provide a muffler in which cross-currents substantially eliminate shell'noise.

A still further object of the present invention is to provide a muffler in which pulsations causing the high speed coasting roar are substantially dissipated.

Further objects and advantages of the present invention will be apparent from the following description,reference being had to the accompanying drawing wherein a pre ferred embodiment of one form of the present '50 invention is clearly shown.

Serial No. 345,492.

In the drawing:

Fig. l is a longitudinal section of the muffler.

Fig. 2 is a side view of the inner exhaust conduit.

tubular member.

Fig. 4 is a transverse section through the muffler along the line 44 of Fig. 1.

Fig. 5 is a view similar to 4 taken along the line 55 of Fig. 1.

Fig. 6 is a view similar to Fig. 4 taken along the line 66 of Fig. 1.

Referring to the drawing, the mufiler is shown comprising three cylinders 20, 30 and 40. The inner cylinder termed the pipe 20, and detailedly illustrated in Fig. 2, has a plurality of elongated slots 21 arranged in helical rows about it and in step formation. The slots are comparatively narrow and long, the longer dimension running longitudinally of the pipe. One end of the pipe is closed by the end cover 22, which is secured within the pipe preferably by welding. The slots circumferential of the tube.

As shown in the Figs. 5 and 6, the slots are arranged in pairs, the slots comprising each pair being diametrically opposite.

The pairs of slots 32 are at ninety degrees to each other, that is, each pair of slots is displaced, circumferentially of the tube 30, ninety degrees from the next adjacent pair of slots.

Fig. 3 shows that the slots 32 are grouped nearer to one end of the tube 30 than the other, thus a comparatively long imperforate surface is provided at the one end of the tube. Referring to Fig. 3, and starting from the bottom end of the tube as regards this figure, the first pair of slots 32 are comparatively close to this end of the tube.

The second pair of slots are spaced comparatively close to the first pair. The third pair of slots are spaced somewhat farther from the second than the second from the first and the fourth still farther from the third than the third from the second, etc. From this it may be seen that the spacing between adjacent pairs of slots widens progressively as the slots approach the upper, imperforate end of the tube.

As shown in the Fig. 1, the tube 30 surrounds the pipe 20. To maintain tube and pipe substantially coaxial, spacer collars 31 are provided which fit snugly about the pipe and into the tube 30. These spacer collars also form end covers for the tube 30. They may be secured upon the pipe and in the tube in any suitable manner, preferably, however, by welding. The relative arrangement between the pipe 20 and tube is such that the comparatively long imperforate end of the pipe 20, which is the open end thereof, is surrounded by the end of the tube 30 at which the slots 32 are more closely grouped or comparing the other ends of the pipe and tube, the end of the pipe 20 more closely approached by the slots 21 is surrounded by the comparatively long imperforate end of the tube 30.

The outer cylinder 40, termed the shell is completely imperforate. Its inside diameter is slightly greater than the outside diameter of the tube 30. Shell surrounds the tube 30 and is maintained substantially coaxial of said tube by spacing collars fitting into each end of the shell and fitting about the ends of the pipe 20, the collars being welded to both the shell and pipe. The one collar fitting about the open end of the pipe 20 and designated by the numeral 41 closes this end of the shell. It has a tubular e2;- tension 43 adapted to receive theexhaust pipe leading from the engine exhaust manifold. The other collar 42, fitting about the end of pipe 20 closed the end cover member 22, is provided with openings 44 through which gases in the shell may vent to atmosphere. A funnel shaped collar 45 is secured in the end of the shell 40, adjacent collar 42, said collar 45 having a tubular extension 46 to which a tail-pipe, not shown, is adapted to be attached.

Sudden effiux of gases under comparatively high pressure, from a pipe will result in the production of noise due to the setting of air into motion by the concentrated gas plug, as it may be termed, issuing suddenly from the end of the pipe. The slots 21 in the pipe 20 cause the gases in the pipe to be emitted progressively so that they tend to set the air surrounding said pipe, into motion with a wedge-like eflort. The gases will tend to discharge from the slots 21 in planes both transversely of the axis of the pipe 20 and longitudinally thereof, thus the gases will move the surrounding air with a wedge-like or shearing effort and consequently resultant noises will be comparatively slight.

Compression of gases in a pipe causes a back pressure to build up, if said compressed gases are not ejected or permitted to escape at a proper rate. The present device provides for the grouping of the slots adjacent the closed end of the pipe 20 so that gases therein may readily escape before they can effect a back pressure. The manner in which the are ejected from slots 21 into the tube '30 providesfor the setting up of turbulence therein which tends to dampen sound.

Gases in the tube 30 must exit through the slots 32 therein. These slots being elongated and circumferential of the tube 30, will cause the gases to be emitted from the tube 30 with the same wedge-like motion in which they were ejected from the )ipe, thus sound or noise is substantially re need in this area of the muffler. This method of ejecting the gases from tube 30 will also set up a turbulence in the shell 40 into which the gases are directed from the tube 30. Shell noise, caused by the impact of gas flow upon the shell is sub stanti ally reduced due to this method of ejecting gases from the tube.

Gases flowing from the slots 21 adjacent the open end of pipe 20 will tend to reverse and flow toward the slots 32 in tube 30, more adjacent the closed end of the shell. The velocity of these flows will be comparatively low, thus the impact with the shell will be insuiiicient to cause shell noise. The velocity of the flows through the succeeding slots 32 will, however, be com aratively higher and thus, the possibility o shell noise is comparatively increased. After the gases have been ejected from the slots 32 adjacent the closed end of the shell, they will flow toward the open end thereof through the annular slot-like space between the shell 40 and tube 30. Combined flows from successive slots 32 will increase said flow through the annular slot-like space causing a cross-current which impinges upon the comparatively higher gas flow through the slots 32 nearer to the open end of the shell, and thus, these flows are diverted and cushioned, consequently they will not strike the shell with sufficient force to cause what is known as shell noise.

From the aforegoing, it will be seen that the present device provides for the mufiiing of noises and the substantial elimination of back pressures by providing the exhaust pipe with elongated slots which cause the gases emitting therefrom to set the surrounding air in motion with a shearing, wedge-like movement, thereby avoiding concussion. The particular arrangement of these elongated slots provides for the reduction of back pressures.

Shell noises are substantially eliminated due to the provision of cross currents and turbulences set up in the comparatively narrow slot-like annular space between the shell 40 and the tube 30, said cross currents and turbulences dampening the effect of the transverse flow of gases emitting from the slots 32.

Roar, caused by the engine being driven at a comparatively high rate with closed throttle, for instance, when descending a steep grade and using the engine as a braking medium, is overcome by the peculiar shape of the slots and their respective locations. The roar which is efiected by pulsations set up by the engine in the exhaust line, is dissipated due to the fact that the slots are elongated, which, as has been described, sets the surrounding air in motion with a shearing, wedge-like effort. The peculiar arrangement of the slots, that is, the slots of the pipe being longit-udinally thereof and the slots of the tube being circumferentially thereof, set up turbulences within the respective portions of the mufiier which tend to dampen the noises causing the roar. The slots of the pipe being arranged nearer to one end of the manifold and the slots of the tube being arranged nearer to the opposite end of the manifold also cause turbulences to be set up within the manifold which, together with the aforementioned turbulences, tends to dampen noises developed within the muflier.

The device may be produced commercially at a minimum expense, it being of simple structure and design, all parts being made up of stampings which may easily be assembled, welding of the parts together providing the necessary rigidity.

Vhile the form of embodiment of the present invention as herein disclosed, constitutes a preferred form, it is to be understood that other forms might be adopted, all coming within the scope of the claims which follow.

What is claimed is as follows:

1. A mufHer for an internal combustion engine, comprising in combination, a casing, tubular members within said casing, one having longitudinally arranged slots, the other having slots arranged circumferentially thereof.

2. A muflier for an internal combustion engine, comprising in combination, an enhaust pipe closed at one end and having slots arranged longitudinally thereof; a tubular member surrounding said pipe, and having slots arranged circumferentially thereof; bafiles closing the end spaces between. the pipe and tubular member; and a casing surrounding the tubular member, said casing being open adjacent the closed end of the exhaust ipe. p 3. A mufiler for an internal combustion engine, comprising in combination, an exhaust pipe open at one end only and having longitudinally arranged slots;

member about the said pipe having circumferentially arranged slots; an imperforate casing about the tubular member; spacer rings at each end of the tubular member fitting about the tubular member and holding" substantially concentric with the pipe and closing the ends of said member; spacer rings in each end of the casing holding the casing substantially concentric with the tubular member.

at. A muffler for an internal combustion engine, comprising in combination, an exhaust pipe open at one end only and having longitudinally arranged slots; a tubular member surrounding the pipe and having circumferentially arranged slots; an imperferate casing surrounding the tubular member; spacer collars upon the pipe holding the tubular member substantially concentric therewith and closing both ends of said tubular member; spacer collars upon the pipe holding the casing substantially concentric with the tubular member, the spacer collar adjacent the closed end of the pipe havin g openings, the other collar closing the end of the casing,

5. A muffler for an internal combustion engine, comprising in combination, an exhaust pipe open at one end only and having helical rows of slots arranged in step formation, the dimension of the slots lengthwise of the pipe being the greater; a tubular member surrounding the pipe having its ends closed and being provided with a plurality of spaced slots, the longer dimensions of which are circumferential of the said member; and an imperforate casing surrounding the tubular member, the end adjacent the closed end of the exhaust pipe being open to atmosphere, the other end being closed.

6. A muffler for an internal combustion engine, comprising in combination, an exhaust pipe open at the one end only and having slots arranged in helical rows the longer dimensions of said slots being longitudinal of the pipe; a tubular member about the pipe coaxial thereof and having spaced slots the longer dimensions of which are circumferential of the member; means for closing both ends of this member; and an imperforate casing about the tubular member, substantially coaxial thereof, closed adjacent the open end of the pipe and open at the opposite end.

7. A mufiler for an internal combustion engine, comprising in combination, an exhaust pipe open at one end only and having rows of slots, the longer dimensions of which are longitudinal of the pipe, said slots extending from close proximity to the closed end of the pipe substantially two-thirds of the way toward the open end. thereof; a tubular memher having centrally recessed end covers adapted to fit over the exhaust pipe forming a cylindrical casing about the pipe, said mema tubularber having slots spaced longitudinally and circumferentially thereof the longer dimensions of the slots being circumferential of the member; and a cylindrical casing surrounding the tubular member, one end thereof being closed, the end adjacent the closed end of the exhaust pipe being open to atmosphere.

S. A muiller comprising in combination, an exhaust pipe closed at one end and having a plurality oi elongated slots grouped nearer to the closed end oi? the pipe; a tube carried by and surrounding the pipe, having both ends closed, and provided with a plurality of elongated slots anguiarly arranged to the slots in the pipe, the slots of the tube being grouped nearer to the open end of the pipe; and an imperforate shell surrounding the tube and supported by the pipe, said sheil being closed at the end adjacent the open end of the pipe.

9. A mufiler comprising in combination, an exhaust pipe closed at one end, and having a plurality of elongated slots, the longer dimensions of which run longitudinally of the pipe, said slot-s being grouped nearer to the closed end of the pipe; a tube of greater t ansverse dimensions than the pipe, supported by said pipe and surrounding it, both ends of the tube being closed, said tube having a plurality of elongated slots, the longer dimensions of which run circumferentially of the tube and which are grouped nearer to the end of the tube supported by the open end of the pipe; and an iinperforate shell of larger diameter than the tube surrounding it and supported by the pipe, one end of the shell being closed.

10. A mufiier comprising in combination, an exhaust pipe closed at one end, and having a plurality of elongated slots, the longer dimensions of which run longitudinally of the pipe, said slots being grouped nearer to the closed end of the pipe a tube of greater transverse dimensions than the pipe, supported by said pipe and surrounding it, both ends of the tube being closed, said tube having a plurality of elongated slots, the longer dimensions of which run circumferentially of the tube, said last mentioned slots being arranged in pairs comprising two diametrically opposite slots, adjacent pairs being displaced at substantially ninety degrees to each other circumferentially of the tube, the slots being grouped nearer to the end of the tube supported at the open end of the pipe; and an imperforate shell surrounding the tube and supported by the pipe, one end of the shell being closed.

11. A muflier comprising in combination, an exhaust pipe closed at one end and having a plurality of elongated slots the longer dimensions of Which run longitudinally of the pipe, said slots being grouped nearer to the closed end of the pipe; a tube of greater transverse dimensions than the pipe, supported by said pipe and surrounding it, both ends of the tube being closed, said tube having a plurality of elongated slots, the longer dimensions of which run circumferentially of the tube, said slots elongated circumferentially of the tube arranged in pairs and grouped nearer to the end of the tube supported at the open end of the pipe, the pairs being spaced so that the distance between adjacent pairs is increased progressively as they approach the end of the tube supported at the closed end of the pipe, said end of the tube being imperforate, and an imperforate shell surrounding the tube, said shell being closed at one end.

In testimony whereof I hereto aifix my signature.

FRED E. ASELTINE. 

